2 * SPDX-License-Identifier: BSD-2-Clause
4 * Copyright (c) 1999 Assar Westerlund
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 #include <sys/cdefs.h>
30 #include <sys/param.h>
31 #include <sys/kernel.h>
33 #include <sys/module.h>
34 #include <sys/mutex.h>
36 #include <sys/resourcevar.h>
38 #include <sys/syscall.h>
39 #include <sys/sysent.h>
40 #include <sys/sysproto.h>
41 #include <sys/systm.h>
42 #include <machine/atomic.h>
45 * Acts like "nosys" but can be identified in sysent for dynamic call
46 * number assignment for a limited number of calls.
48 * Place holder for system call slots reserved for loadable modules.
51 lkmnosys(struct thread *td, struct nosys_args *args)
54 return (nosys(td, args));
58 lkmressys(struct thread *td, struct nosys_args *args)
61 return (nosys(td, args));
64 struct sysent nosys_sysent = {
65 .sy_call = (sy_call_t *)nosys,
66 .sy_systrace_args_func = NULL,
68 .sy_flags = SYF_CAPENABLED,
69 .sy_auevent = AUE_NULL,
70 .sy_entry = 0, /* DTRACE_IDNONE */
72 .sy_thrcnt = SY_THR_STATIC,
76 syscall_thread_drain(struct sysent *se)
78 u_int32_t cnt, oldcnt;
81 oldcnt = se->sy_thrcnt;
82 KASSERT((oldcnt & SY_THR_STATIC) == 0,
83 ("drain on static syscall"));
84 cnt = oldcnt | SY_THR_DRAINING;
85 } while (atomic_cmpset_acq_32(&se->sy_thrcnt, oldcnt, cnt) == 0);
86 while (atomic_cmpset_32(&se->sy_thrcnt, SY_THR_DRAINING,
92 syscall_thread_enter(struct thread *td, struct sysent **se)
94 u_int32_t cnt, oldcnt;
96 KASSERT(((*se)->sy_thrcnt & SY_THR_STATIC) == 0,
97 ("%s: not a static syscall", __func__));
100 oldcnt = (*se)->sy_thrcnt;
101 if ((oldcnt & (SY_THR_DRAINING | SY_THR_ABSENT)) != 0) {
105 cnt = oldcnt + SY_THR_INCR;
106 } while (atomic_cmpset_acq_32(&(*se)->sy_thrcnt, oldcnt, cnt) == 0);
111 syscall_thread_exit(struct thread *td, struct sysent *se)
113 u_int32_t cnt, oldcnt;
115 KASSERT((se->sy_thrcnt & SY_THR_STATIC) == 0,
116 ("%s: not a static syscall", __func__));
119 oldcnt = se->sy_thrcnt;
120 cnt = oldcnt - SY_THR_INCR;
121 } while (atomic_cmpset_rel_32(&se->sy_thrcnt, oldcnt, cnt) == 0);
125 kern_syscall_register(struct sysent *sysents, int *offset,
126 struct sysent *new_sysent, struct sysent *old_sysent, int flags)
130 if ((flags & ~SY_THR_STATIC) != 0)
133 if (*offset == NO_SYSCALL) {
134 for (i = 1; i < SYS_MAXSYSCALL; ++i)
135 if (sysents[i].sy_call == (sy_call_t *)lkmnosys)
137 if (i == SYS_MAXSYSCALL)
140 } else if (*offset < 0 || *offset >= SYS_MAXSYSCALL) {
142 } else if (sysents[*offset].sy_call != (sy_call_t *)lkmnosys &&
143 sysents[*offset].sy_call != (sy_call_t *)lkmressys) {
144 KASSERT(sysents[*offset].sy_call != NULL,
145 ("undefined syscall %d", *offset));
149 KASSERT(sysents[*offset].sy_thrcnt == SY_THR_ABSENT,
150 ("dynamic syscall is not protected"));
151 *old_sysent = sysents[*offset];
152 new_sysent->sy_thrcnt = SY_THR_ABSENT;
153 sysents[*offset] = *new_sysent;
154 atomic_store_rel_32(&sysents[*offset].sy_thrcnt, flags);
159 kern_syscall_deregister(struct sysent *sysents, int offset,
160 const struct sysent *old_sysent)
165 return (0); /* XXX? */
167 se = &sysents[offset];
168 if ((se->sy_thrcnt & SY_THR_STATIC) != 0)
170 syscall_thread_drain(se);
171 sysents[offset] = *old_sysent;
176 syscall_module_handler(struct module *mod, int what, void *arg)
179 return (kern_syscall_module_handler(sysent, mod, what, arg));
183 kern_syscall_module_handler(struct sysent *sysents, struct module *mod,
186 struct syscall_module_data *data = arg;
187 modspecific_t ms = { 0 };
192 error = kern_syscall_register(sysents, data->offset,
193 data->new_sysent, &data->old_sysent, data->flags);
195 /* Leave a mark so we know to safely unload below. */
199 ms.intval = *data->offset;
201 module_setspecific(mod, &ms);
204 error = data->chainevh(mod, what, data->chainarg);
208 * MOD_LOAD failed, so just return without calling the
209 * chained handler since we didn't pass along the MOD_LOAD
212 if (data->offset == NULL)
214 if (data->chainevh) {
215 error = data->chainevh(mod, what, data->chainarg);
219 error = kern_syscall_deregister(sysents, *data->offset,
224 return (data->chainevh(mod, what, data->chainarg));
232 syscall_helper_register(struct syscall_helper_data *sd, int flags)
235 return (kern_syscall_helper_register(sysent, sd, flags));
239 kern_syscall_helper_register(struct sysent *sysents,
240 struct syscall_helper_data *sd, int flags)
242 struct syscall_helper_data *sd1;
245 for (sd1 = sd; sd1->syscall_no != NO_SYSCALL; sd1++) {
246 error = kern_syscall_register(sysents, &sd1->syscall_no,
247 &sd1->new_sysent, &sd1->old_sysent, flags);
249 kern_syscall_helper_unregister(sysents, sd);
258 syscall_helper_unregister(struct syscall_helper_data *sd)
261 return (kern_syscall_helper_unregister(sysent, sd));
265 kern_syscall_helper_unregister(struct sysent *sysents,
266 struct syscall_helper_data *sd)
268 struct syscall_helper_data *sd1;
270 for (sd1 = sd; sd1->registered != 0; sd1++) {
271 kern_syscall_deregister(sysents, sd1->syscall_no,